1. Field of the Invention
This invention relates to a method for carrying out power source voltage check for a camera which is suited particularly for a lens shutter type camera. The term "power source voltage check" as used herein for the purpose of this invention includes two modes of action, one being to make display only when the power source voltage drops below a prescribed value and the other to inhibit the photo-taking operation of the camera under such a condition.
2. Description of the Prior Art
In checking the voltage of a power source, the conventional cameras have been arranged to ensure the accuracy of the power source voltage check by allowing either the real maximum load current of the camera or an imitative load current which corresponds to the maximum load current to flow. In other words, they are arranged to accurately check a power source voltage with the flow of the maximum load current without being affected by the characteristic of the power source battery which tends to fluctuate with the current value. Meanwhile, the power source voltage check is preferably performed when the power source has become stable after a power supply switch is turned on and before commencement of a sequence of photographing actions because the sequence of photographing actions should be inhibited to prevent the camera from performing an erroneous action when the power source battery is defective.
In most cases, the maximum load current is required by a starting magnet or a shutter controlling magnet. When a current is allowed to flow to such a magnet for the purpose of checking the power source voltage, the sequence of photographing actions would begin and shutter release might be effected if there is provided no mechanical restriction arrangement in the camera.
To prevent such erroneous actions, therefore, a mechanical restriction mechanism is often arranged to prevent the action of the armature of a magnet before a shutter release operation of the camera. However, the provision of such a mechanism not only complicates the structural arrangement of the camera, thus resulting in an increased cost of manufacture, but also presents great difficulty in arranging it within a severely limited space available in a lens shutter camera.
Meanwhile, the above-stated conventional method of having a current flow to a discrete imitative load arrangement corresponding to the maximum or largest load of the camera, it is difficult to consume within an IC arrangement the current which corresponds to the maximum load current. It is conceivable to avoid that difficulty by connecting an external element for imitative load control to a pin of an IC discretely provided for that purpose. However, such an alternative is disadvantageous in terms of actual electrical arrangements and also with respect to increase in cost of the product.